Predictive maintenance has been a long and never-ending quest, and not just in industrial automation. A study by GE and Accenture holds up to executives predictive maintenance as the key to lowering maintenance costs up to 30 percent and slashing up to 70 percent of production line downtime caused by equipment breakdowns. As Industry 4.0 evolves from theory to actual working applications, a golden age of predictive maintenance may finally be dawning. That’s because the same industrial networks needed to connect production and factory equipment and make them more intelligent also provides the nervous system for communicating vital information about the health of machine components.
For example, a not uncommon concern of pneumatic motion systems is a voltage sag on long wiring runs that may cause valve misfires and quality problems. If voltage sensors on the valve manifolds are wired to the factory network, then a voltage sag might be easily identified as the source of the problem. Another example a component that is nearing the end of its expected cycle count being replaced during planned downtime instead of during an unexpected shut down.
For intelligent manufacturing plants to utilize data for predictive maintenance, the network needs to receive sensor data. Many machine components already have ways to communicate with the factory network via protocols such as Ethernet/IP, EtherCAT and PROFINET. The challenge is the high cost of bringing Industrial Ethernet communication, both wiring and provisioning, all the way to the many sensor nodes. What industry needs for the Industry 4.0 revolution is a practical protocol for connecting sensors to the network. Fortunately, simple serial protocols such as IO-Link have emerged, providing easily provisioned, low-cost communication at the edge.
With this potential in mind, it will be worthwhile to explore the characteristics that IO-Link advocates cite for their enthusiasm.
IO-Link Stands Out From the Crowd
IO-Link, also known by its not-so-catchy acronym SDCI (Single-Drop Digital Communication), has moved to the front of a crowd of longer established open-communication protocols as being a powerful yet cost-effective open protocol well aligned with Industry 4.0. It enables simple, point-to-point, scalable communications between sensors or actuators and the motion controller. IO-Link is the first I/O technology for communicating with machine sensors and actuators to be adopted as an international standard (IEC 61131-9). In a way it is like having an industrial USB, a universal standard that will bring the IIoT (Industrial Internet of Things) down to the component level.
Typically, the factory floor is inhabited by large controller cabinets that house PLCs along with I/O cards and many I/O terminations. These create the interfaces for all machine-to-machine communication. A nice benefit of IO-Link is that it allows much of the interface to be moved out onto the machine, significantly reducing cabinet space that consumes precious plant floor real estate.
This is achieved by establishing communication via an IO-Link master block situated closer to the point of sensing, therefore greatly simplifying the communications and cabling arrangement. IO-Link’s IP67-rated master blocks have a significantly reduced cost compared to using IP67-rated Ethernet blocks for on-machine I/O.
Wiring is labor intensive. Versus discrete wiring, IO-Link master blocks and architecture significantly reduce the amount of wiring needed between pneumatic manifolds and sensors, and likewise reduce the number of interconnections. This approach enhances overall reliability, as every point of interconnection represents a potential point of failure. What’s more, IO-Link uses standard non-shielded M12 cables and connectors having just three or five wires. They offer many reliability and implementation advantages compared to the traditional 25-pin/D-sub connectors that are commonly used to wire machine components and systems.
At the commissioning stage, IO-Link enables rapid troubleshooting that a technician can perform locally or remotely. It’s also more straightforward to detect, isolate and resolve snags such as false sensor settings.
Compared to a centralized, proprietary approach, IO-Link uses a decentralized model that delivers real cost benefits, both in terms of the initial cost of the required hardware, and in terms of the labor cost needed to install and connect hardware.
Another benefit of a plug-and-play decentralized topology is flexibility. As IO-Link is vendor neutral, engineers have the freedom to combine devices and modules from different suppliers. Engineers can extend and modify existing implementations easily, simply by adding more sensors. This ability to change control and monitoring goes a long way toward Industry 4.0’s promise of the smooth reconfiguration of production environments. Reconfiguration is fast, and the risk is low, compared to complex, vendor-tied approaches. Some experts believe that in the IIoT there’s no place for proprietary solutions. Rather, interoperability with third party devices via an open, exchange-based architecture is essential.
Not all machine locations are free of vibration, moisture and other environmental threats such as dust and swarf. Such conditions can damage the reliability of the communication infrastructure installed to control and monitor processes. IO-Link uses non-shielded, five-pin proximity switch cables and connectors that are robustly designed specifically for industrial applications. Typically, they have either IP65 or IP67 ratings, indicating their ability to perform reliably in a wide range of operating environments. In addition, as all IO-Link data transfer is based on a 24-volt signal (compared to about 1 volt for standard Ethernet), its immunity to electrical interference is very high. The screened cables and grounding needed with some other approaches is not necessary with IO-Link.
The major benefits of deploying IO-Link are to be enjoyed during the day-to-day working life of the application. With easily extendable and multiple sensing points, IO-Link makes it easy to collect extensive and precise data at the machine, and then easily communicate that data in real time, enabling close monitoring of component health and manufacturing.
When a sensor reports an excursion from adjustable pre-set parameters, the programming in the PLC or motion controller can trigger an alarm, so that problems are addressed promptly, before there is an unplanned interruption of production, and before there is a compromise in product quality. In many cases, early sensor notification of potential maintenance problems will allow system operators to research, evaluate, and schedule the necessary corrective maintenance for a time when manufacturing can be stopped, such as a planned plant maintenance shutdown, or overnight, when throughput demand is low.
The desire for higher performance, productivity and efficiency is driving the move to Industry 4.0. This includes the ability to foresee problems and proactively plan maintenance work. High levels of predictive maintenance are only possible if managers deploy a suitable communications infrastructure all the way down to the machine components. IO-Link is gaining popularity as an ideal connection to edge devices, based on its ability to deliver a robust, low-cost, easily-installed solution.
Rich McDonnell is Market Development Manager of Pneumatic Division, Motion Systems Group at Parker Hannifin.